Just wanted to say that we've been having the same situation for a couple of hours now. However, so far as I can tell, it seems to have been resolved for both of our sites in the last few minutes without me having changed anything, so I'm guessing it was just a brief glitch in the Card validator or something.

Again if there are specific pages and links that exhibit and issue please share as we cannot help otherwise.

We don't have lots of bandwidth to help debug individual pages so the troubleshooting post and pages are intended to help self-diagnose. Please let us know what you've tested before reporting issues. Thank you!

I was testing with our own site as we are new to twitter cards in order to solve an issue on a clients site

It is a wordpress site and we have set the cards up using the social settings in seo yoast. The cards work and display fine in the validator for all pages except the home page. On checking the source as in the troubleshooting guide the home page is missing the correct tags that appear on the page sources for the other pages.

I am unsure why it works on all pages except the home page.

Is it possible you could help us have the card appear for the home page as well as the others please?